Conveyorized work supporting tables having bristle blocks forming the work supporting surface typically include a vacuum holddown system to create an air pressure difference between an upper surface of the work material or overlay material supported on bristle blocks and the pressure at an upper surface of the bristle blocks. Atmospheric pressure at the upper surface of the work material or overlay material is higher than that at a lower surface of the work material or overlay sheet supported on the upper surface of the bristle blocks so that the work material to be conveyed along the table is drawn downwardly toward and into secure engagement with the upper surface of the bristle blocks to prevent sliding of the work material over the bristle blocks. An air impermeable overlay sheet typically covers the work material to further prevent shifting of the work material, and more particularly, to prevent several plies of work material from shifting relative to each other. Maintaining registration among several plies of work material is critical when, for example, the plies are to be cut as a unit along a conveyorized cutting device. Such conveyors typically further include stationary side seals in the form of elongated strips of air impermeable material which are coupled to side members of the conveyorized table and which extend inwardly over a portion of the bristle blocks. An outward portion of the overlay sheet slides along an upper surface of the stationary side seal while an inward portion of the overlay sheet is held securely against the adjacent bristle blocks and the work material by the pressure difference between upper and lower surfaces of the overlay sheet generated by the vacuum holddown system. A drawback with this side seal assembly is that mechanical shear experienced by bristles by rubbing against the stationary side seal at an interface line defined by the boundary of the side seal and the bristle blocks causes the overlay sheet to stretch and create a wrinkle or crease. The crease created in the overlay sheet near the interface line causes the bristles to part or bend inwardly of the table such that the creased portion of the overlay sheet is drawn downwardly into the bristles forming a crevice. Crevicing of the overlay sheet near the interface line can lead to jamming of the overlay sheet with a take-off ramp of the conveyorized table. Another drawback is that a portion of the overlay sheet in the vicinity of the interface line slides along the stationary seal and thus is not securely held down thereto to prevent the portion of the overlay sheet over the side seal from being drawn inwardly toward and downwardly into the adjacent bristle blocks.
It is therefore an object of the present invention to provide a side seal assembly for a conveyorized table with vacuum holddown which significantly minimizes an overlay sheet from being drawn downwardly into bristle blocks at an interface of the bristle blocks and a side seal.
Other objects of the present invention will be made apparent from the following description and accompanying drawings.